I am just setting up a brand new AR7100R receiver but I can't get the sensor light to light from the back plate sensor. I have taken the sensor off and I can get it to light but only if I touch it on something metal, then sometimes the light will STAY ON and will go OFF when I touch it on something metal! Any ideas anyone?

You could have a bad sensor...
Have you tried turning it with the starter?
For mine it barely touches the back plate and it shows up when turning by hand (os55)

spending time, paying attention

No just by hand and ive tried with it touching the back plate and with a 0.5-1mm gap as the manual suggest for YS engines. I think the magnet has just got too weak. The Receiver was NIB but it could actually be quite old so the magnet could have lost its power.

After doing some research it seems some ys 91's have a steel lined back plate so the sensor won't work. I'll check today if mine has or not, it's the 91srs, black head?

60% of the time, it works every time!

Ha so it turns out the 91SRS has the thick steel plate behind the back plate or possibly 300 series stainless as it would put the sensor light on permanently if it was magnetic. Anyway I have an old 91ST so I swapped back plates as the ST doesn't have the steel plate and it works!!

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